This application claims priority to the filing date of German Utility Model Application No. 203 08 665.1 filed Jun. 3, 2003.
1. Field of the Invention
The invention relates to an inner rotor electric motor comprising a stator core having an annular stator back yoke and a plurality of stator poles. The stator poles project radially inwards from the inner surface of the stator back yoke. The stator core encloses an assembly consisting of a shaft and a rotor, the shaft and the rotor being rotatably supported in respect of the stator by means of roller bearings.
The invention relates in general to the field of electronically commutated brushless direct current motors and other permanent magnet motors that are configured as inner rotor motors.
2. Background of the Invention
Such motors known from the prior art comprise a shaft, a rotor assembly having a magnetically soft back yoke and one or several permanent magnets disposed on it, and a stator assembly including a stator core composed of laminations, for example, and phase windings. Two bearings are arranged on the shaft on each side of the rotor assembly at an axial distance from each other to journal the rotor assembly in respect of the stator assembly. The electric motor according to the invention is not limited to any specific application and can be used in the automotive sector, for example, to support the steering, to operate the windscreen wipers or to drive a cooling water pump just as it can be used as a drive motor for fans, disk drives, machine tools or suchlike.
Inner rotor motors have the basic disadvantage that due to the cylinder-shaped, closed stator, they have to be mounted in an axial direction which involves limitations for inserting and adjusting the components inside the stator. The cause of this is the magnetic forces that work in an axial and radial direction between the stator and the permanent magnets of the rotor. Moreover, it is difficult to apply the phase windings to the stator poles of a stator core. For this purpose, highly complex winding techniques and machines, such as needle winders, are used.
The object of the invention is to provide an inner rotor electric motor that is easy to manufacture and to assemble.